The present invention relates generally to a hole cutting apparatus and more particularly to a portable apparatus, that is, one which can be utilized in the field, for cutting a hole through the sidewall of a longitudinally extending pipe using a cylinder or hole saw for accomplishing this.
Under certain circumstances, it is necessary to tap into an existing section of pipe at some point along its length. This requires that a hole be cut through the sidewall of the pipe at the point of connection and a cross pipe of some sort be assembled in sealing engagement about this hole. In one conventional method of doing this, the hole is cut through the sidewall of the pipe utilizing a cylinder saw blade. This blade is typically supported on and driven by a conventional drill rig which, except for axial movement, is fixed in place. Because the hole can be provided with great precision, the cross pipe, that is the pipe to be tapped in place, can be accurately positioned around the opening, in many cases without the utilization of special sealing gaskets or the like. While this particular method is quite satisfactory for its intended purpose, it is extremely difficult to carry it out in the field since the drill rig used to support and guide the cylinder saw blade is quite large and cumbersome. As an alternative in the field, it has heretofore been common practice to utilize a keyhole saw to provide the appropriately sized opening for tap-in purposes. One drawback with this approach is that it is time consuming and a more serious drawback is that the hole itself is not usually accurately provided. In order to compensate for this, it has been the general practice to provide additional sealing means around the tap-in connection and in most cases a saddle strapped around the main pipe and supporting the tapped-in pipe is often necessary.
As will be seen hereinafter, the present invention is directed to an apparatus, specifically a portable apparatus, which can be readily used in the field for supporting and guiding a cylinder saw blade used in cutting a hole through the sidewall of a longitudinally extending pipe, thereby eliminating the various drawbacks discussed above.